<p>The R4000, a highly integrated, 64-b RISC microprocessor that provides a simple solution to the increasing demands on the size of address space while maintaining full compatibility with previous Mips processors, is described. The microprocessor's on-chip central processing unit, floating point unit, memory management unit, primary caches, system interface logic, secondary cache control logic with flexible interface, the programmable system interface for high-performance multiprocessor servers and low-cost desktop systems, the flexible multiprocessor support, and the 1.2 million transistors implemented in CMOS technology are discussed. The R4000's superpipelining techniques allow it to process more instructions simultaneously than the previous generation of microprocessors. It is shown that, according to SPEC benchmark tests, it achieves the highest performance of any microprocessor chip</p>